One really dead cylinder

kmead

kmead

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kmead
A Malibu had a rough engine and a big loss of power yesterday. I sent our Malibu and a Mechanic out to find the problem and he found it. The valve head snapped off and imbedded itself into the #3 cylinder piston. I haven't seen anything like this for 20 years.

Kevin
 

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I don't know the cylinder total time, it's often hard to know. It does have about 450 hrs since a repair. I don't know what was replaced when the repair was done. In my opinion I think either the valve failed or the valve stuck open the the piston broke it off.

Metal in the engine now. I think it's time for an overhaul or exchange. These money pits called airplanes never stop.

Kevin
 
I don't know the cylinder total time, it's often hard to know. It does have about 450 hrs since a repair. I don't know what was replaced when the repair was done. In my opinion I think either the valve failed or the valve stuck open the the piston broke it off.

Metal in the engine now. I think it's time for an overhaul or exchange. These money pits called airplanes never stop.

Kevin
 
kmead said:
I don't know the cylinder total time, it's often hard to know. It does have about 450 hrs since a repair. I don't know what was replaced when the repair was done. In my opinion I think either the valve failed or the valve stuck open the the piston broke it off.

Metal in the engine now. I think it's time for an overhaul or exchange. These money pits called airplanes never stop.

Kevin
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Wow.. sorry to hear that.

:sad:
 
kmead said:
A Malibu had a rough engine and a big loss of power yesterday. I sent our Malibu and a Mechanic out to find the problem and he found it. The valve head snapped off and imbedded itself into the #3 cylinder piston. I haven't seen anything like this for 20 years.

Kevin
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Typical Lycoming failure, I'll wager it had morning sickness long before failure.
 
kmead said:
A Malibu had a rough engine and a big loss of power yesterday. I sent our Malibu and a Mechanic out to find the problem and he found it. The valve head snapped off and imbedded itself into the #3 cylinder piston. I haven't seen anything like this for 20 years.

Kevin
Click to expand...

It will buff right out. :D
 
I have heard the phrase used to describe aged lifters which take a while to pump up.
 
Let'sgoflying! said:
I have heard the phrase used to describe aged lifters which take a while to pump up.
Click to expand...

who ever used that term in that manor doesn't understand the valve train.

A poor lifter will collapse when the engine is hot and the oil leaks out of the hydraulic unit, a valve that will not close until the engine heats up is morning sickness. The valve stem is usually coated with lead and will not fit into the guide until the guide expands

Any hydraulic unit use in aviation is known as a zero lash lifter, it will operate the valve even when completely collapsed, all the hydraulic unit will do is close the gap in the valve train.
 
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Reminds me of my Mom's Fiat 124 Spider - pounded valve head right through the piston!
 
kmead said:
A Malibu had a rough engine and a big loss of power yesterday. I sent our Malibu and a Mechanic out to find the problem and he found it. The valve head snapped off and imbedded itself into the #3 cylinder piston. I haven't seen anything like this for 20 years.

Kevin
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AW Man................... That hurts just looking at that pic.:hairraise::cryin:

Ben.
 
Tom mentioned Morning Sickness. Sometimes a valve gets enough crud on its stem to make it stick in the guide once it cools off. If it was open when the engine stopped, it'll stick open and that cylinder will have no compression and the engine will run lumpy until it warms up a little. If it sticks closed it can bend the valve pushrod, visible as a bent pushrod tube. Lots worse than one sticking open. I don't know, but Tom might, whether the piston in a 540 comes up high enough to strike a valve that's stuck open.

Engine that fly infrequently or on short flights can suffer corrosion; the valve stems have been known to get pitted and weakened enough to break.

Dan
 
The real question is how to not allow morning sickness to lead to a failure?
 
kmead said:
A Malibu had a rough engine and a big loss of power yesterday. I sent our Malibu and a Mechanic out to find the problem and he found it. The valve head snapped off and imbedded itself into the #3 cylinder piston. I haven't seen anything like this for 20 years.

Kevin
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I did that to a Fiat 650 in 1989. My brother was NOT happy :incazzato:.
 
Tom-D said:
The real question is how to not allow morning sickness to lead to a failure?
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Over at Cessna Pilots Assn., and with the disclaimer that I am not a mechanic, they recommend using the "rope technique" to remove the valve with the cylinder still on, ream out the valve guide, and reinsert from the inside.

Takes a bit of doing, and a steady hand, but the cylinder doesn't have to be removed at all.

Here's someone else's photos (better ones at CPA in their forum) of the same process...

http://www.theleftseat.net/stickyvalvereaming.html

Talked to a friend who had to do this on his O-200 on a C-150. He has one of those mythical "friendly IA's" who'll do work on the aircraft in the shade of the overhanging cover outdoors... and he'd had a valve stick open *in-flight* three times. After trying various other remedies, they reamed the guide, and the "little O-200 that could"... is back to could'ing. :)

The mechanic says the culprit is 100LL in the above case of the O-200... a little valve guide wear, a whole lot of "lead" (it's not really lead anymore) blowing up there and getting between the valve guides and the valve and all over everything and becoming "sticky" at shutdown when the temperature falls.

Note for this: As someone pointed out, *some* engines are non-interference... the valve can stick all the way open and the piston won't ever hit it. Other engines are tighter and have built in interference... the valve will be struck by the piston if it sticks open.

If the valve is damaged, you're stuck having to pull the cylinder and do a valve-job/top-overhaul.

Finding a mechanic who's done it (or in the case of my friend, a mechanic who'd always wanted to try it and was willing to pull the whole jug if they got into trouble trying!), is one part of it...
 
denverpilot said:
Over at Cessna Pilots Assn., and with the disclaimer that I am not a mechanic, they recommend using the "rope technique" to remove the valve with the cylinder still on, ream out the valve guide, and reinsert from the inside.

Takes a bit of doing, and a steady hand, but the cylinder doesn't have to be removed at all.

Here's someone else's photos (better ones at CPA in their forum) of the same process...
Click to expand...
If anyone is interested I can post my writeup from the CPA forum here regarding the "rope trick".
 
Does this have to be an FAA Certified and Approved "rope"? :D I love shade tree mechanic'in, being the grandson of a frugal (by necessity) German farmer and the son of a construction company owner.
 
gkainz said:
Does this have to be an FAA Certified and Approved "rope"? :D I love shade tree mechanic'in, being the grandson of a frugal (by necessity) German farmer and the son of a construction company owner.
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The only purpose of the rope is to hold the valve against the eat so the keepers and springs can be removed. Air pressure works, too, but someone has to hold the prop still near TDC.

The air doesn't have to be FAA-approved.

Dan
 
Dan Thomas said:
The only purpose of the rope is to hold the valve against the eat so the keepers and springs can be removed. Air pressure works, too, but someone has to hold the prop still near TDC.

The air doesn't have to be FAA-approved.

Dan
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Neither does the rope or the snap-on ball peen hammer.
 
Any hydraulic unit use in aviation is known as a zero lash lifter, it will operate the valve even when completely collapsed, all the hydraulic unit will do is close the gap in the valve train.
Click to expand...

Tom does that mean a collapsed lifter will allow the valve to open properly, and the cylinder to fire normally? And that an engine with a collapsed lifter will run smoothly?

I had figured the person who said this meant that when the engine stopped, the valve spring was pressing on the valve train, pushing the oil out of a worn lifter til the pressure was off......then on start up the deflated lifter was taking a moment to pump up again.
 
I think we need a General Counsel Official Opinion letter on certification needed for the rope. :D

BTW, yeah, I'm familiar with the rope trick - works in regular automotive engines as well. Like I said, grandson of a very ingenious and industrious (and frugal) farmer. He modified standard, typical 1930s farm equipment into power line construction equipment when the Rural Electrical Association came into existence and was instrumental in the initial electrification of a lot of Minnesota and North Dakota.
 
Let'sgoflying! said:
Tom does that mean a collapsed lifter will allow the valve to open properly, and the cylinder to fire normally? And that an engine with a collapsed lifter will run smoothly?

I had figured the person who said this meant that when the engine stopped, the valve spring was pressing on the valve train, pushing the oil out of a worn lifter til the pressure was off......then on start up the deflated lifter was taking a moment to pump up again.
Click to expand...

The travel of the lifter's internal piston is really small, not nearly enough to leave the valve shut when it's bottomed out and the cam lifts the lifter all the way. Lycoming's dry tappet clearance spec is .028 to .080", reflecting the movement of the tappet's piston, and the cam lift (which they don't specify in the manual, strangely) will be .300" or more.

Dan
 
Let'sgoflying! said:
Tom does that mean a collapsed lifter will allow the valve to open properly, and the cylinder to fire normally? And that an engine with a collapsed lifter will run smoothly?

I had figured the person who said this meant that when the engine stopped, the valve spring was pressing on the valve train, pushing the oil out of a worn lifter til the pressure was off......then on start up the deflated lifter was taking a moment to pump up again.
Click to expand...

AFaIK, the only symptom of collapsed lifters is the clattering noise which might not be heard in the cockpit.
 
Let'sgoflying! said:
Tom does that mean a collapsed lifter will allow the valve to open properly,
No.
and the cylinder to fire normally?
Yes,
And that an engine with a collapsed lifter will run smoothly?
in theory no, but you can't tell the difference

I had figured the person who said this meant that when the engine stopped, the valve spring was pressing on the valve train, pushing the oil out of a worn lifter til the pressure was off......then on start up the deflated lifter was taking a moment to pump up again.
Click to expand...

that lifter will fill with oil on the first time it hits top dead center, IOW 1 rotation of the engine will fill that lifter with oil. Remember oil is flowing thru that lifter hydraulic unit under pressure to oil the upper cylinder rocker shafts and valve guides.
 
What's the most important part of the rope?
 
gkainz said:
"The knot on the bitter end, Chief!"
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yep, you drop that rope into the cylinder your in for a days frustration. "Well I almost had it that time" will become a very familiar phrase.
 
The rope trick works better for me than the air. A flat lifter really shows itself at high RPM (take-off). An engine monitor will show a sudden drop in EGT on the problem cylinder as soon as you feel the miss and roughness. On a TSIO 520/550 you will think it's going to quit. When you pull the power back for cruise climb it goes away. The flat lifter also stops the flow of oil to the rest of it's own push rod, rocker arm, and valve too.

Kevin
 
kmead said:
The rope trick works better for me than the air. A flat lifter really shows itself at high RPM (take-off). An engine monitor will show a sudden drop in EGT on the problem cylinder as soon as you feel the miss and roughness. On a TSIO 520/550 you will think it's going to quit. When you pull the power back for cruise climb it goes away. The flat lifter also stops the flow of oil to the rest of it's own push rod, rocker arm, and valve too.

Kevin
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If your lifter won't pump up at idle, your problems are way beyond a bad lifter.
 
Tom-D said:
What is the danger of doing it Lycomings Way?
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Seeing as no one has jumped on this question, I suggest you read the Lycoming service bulletin and see where it says to clean the lead out of the guide or off the stem of the valve..
 
Tom-D said:
Seeing as no one has jumped on this question, I suggest you read the Lycoming service bulletin and see where it says to clean the lead out of the guide or off the stem of the valve..
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Lycoming 388C and 1425A both refer to reaming the valve guide to remove the lead build up.
http://www.lycoming.textron.com/support/publications/service-bulletins/pdfs/SB388C.pdf - Section 9b on page 10
http://www.lycoming.textron.com/support/publications/service-instructions/pdfs/SI1425a.pdf - Section 10 on page 3

If the valve stem concerns you it is possible to maneuver the stem out through the spark plug hole and inspect it. Or so I'm told. I just looked at mine through the plug hole.

I suppose their could be buildup on the valve stem that might prevent it from allowing the valve to close completely, but a quick compression test should show that after you have completed the work.

Is that what you are asking about?
 
NC Pilot said:
Lycoming 388C and 1425A both refer to reaming the valve guide to remove the lead build up.
http://www.lycoming.textron.com/support/publications/service-bulletins/pdfs/SB388C.pdf - Section 9b on page 10

And if it goes in freely you don't ream.. why not?

http://www.lycoming.textron.com/support/publications/service-instructions/pdfs/SI1425a.pdf - Section 10 on page 3

Again a reamer, why not a hone or any other method of cleaning all the lead out of the guide.

If the valve stem concerns you it is possible to maneuver the stem out through the spark plug hole and inspect it. Or so I'm told. I just looked at mine through the plug hole.

If you do that in a Lycoming what is the result, you get a nice clean valve, OK, BUT....

I suppose their could be buildup on the valve stem that might prevent it from allowing the valve to close completely, but a quick compression test should show that after you have completed the work.

Is that what you are asking about?
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I'm not asking, I'm trying to point out that Lycoming does not want you to clean all the lead out of the guide nor do they want you to clean it off the valve, Why Not.
 
I assume this is a quiz ... I will guess

B. Lead and carbon deposits on valve stem seal the guide and prevent combustion gases from leaking up the valve guide

but I'm talking thru my hat on that one...
 
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